+ mm-move-page-deferred_list-to-folio-_deferred_list.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: move page->deferred_list to folio->_deferred_list
has been added to the -mm mm-unstable branch.  Its filename is
     mm-move-page-deferred_list-to-folio-_deferred_list.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-move-page-deferred_list-to-folio-_deferred_list.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: mm: move page->deferred_list to folio->_deferred_list
Date: Wed, 11 Jan 2023 14:29:10 +0000

Remove the entire block of definitions for the second tail page, and add
the deferred list to the struct folio.  This actually moves _deferred_list
to a different offset in struct folio because I don't see a need to
include the padding.

This lets us use list_for_each_entry_safe() in deferred_split_scan()
and avoid a number of calls to compound_head().

Link: https://lkml.kernel.org/r/20230111142915.1001531-25-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/huge_mm.h  |    9 ++++-----
 include/linux/mm_types.h |   14 ++++++++------
 mm/huge_memory.c         |   32 +++++++++++++++-----------------
 3 files changed, 27 insertions(+), 28 deletions(-)

--- a/include/linux/huge_mm.h~mm-move-page-deferred_list-to-folio-_deferred_list
+++ a/include/linux/huge_mm.h
@@ -295,11 +295,10 @@ static inline bool thp_migration_support
 
 static inline struct list_head *page_deferred_list(struct page *page)
 {
-	/*
-	 * See organization of tail pages of compound page in
-	 * "struct page" definition.
-	 */
-	return &page[2].deferred_list;
+	struct folio *folio = (struct folio *)page;
+
+	VM_BUG_ON_FOLIO(folio_order(folio) < 2, folio);
+	return &folio->_deferred_list;
 }
 
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
--- a/include/linux/mm_types.h~mm-move-page-deferred_list-to-folio-_deferred_list
+++ a/include/linux/mm_types.h
@@ -141,12 +141,6 @@ struct page {
 		struct {	/* Tail pages of compound page */
 			unsigned long compound_head;	/* Bit zero is set */
 		};
-		struct {	/* Second tail page of transparent huge page */
-			unsigned long _compound_pad_1;	/* compound_head */
-			unsigned long _compound_pad_2;
-			/* For both global and memcg */
-			struct list_head deferred_list;
-		};
 		struct {	/* Second tail page of hugetlb page */
 			unsigned long _hugetlb_pad_1;	/* compound_head */
 			void *hugetlb_subpool;
@@ -302,6 +296,7 @@ static inline struct page *encoded_page_
  * @_hugetlb_cgroup: Do not use directly, use accessor in hugetlb_cgroup.h.
  * @_hugetlb_cgroup_rsvd: Do not use directly, use accessor in hugetlb_cgroup.h.
  * @_hugetlb_hwpoison: Do not use directly, call raw_hwp_list_head().
+ * @_deferred_list: Folios to be split under memory pressure.
  *
  * A folio is a physically, virtually and logically contiguous set
  * of bytes.  It is a power-of-two in size, and it is aligned to that
@@ -368,6 +363,13 @@ struct folio {
 			void *_hugetlb_hwpoison;
 	/* private: the union with struct page is transitional */
 		};
+		struct {
+			unsigned long _flags_2a;
+			unsigned long _head_2a;
+	/* public: */
+			struct list_head _deferred_list;
+	/* private: the union with struct page is transitional */
+		};
 		struct page __page_2;
 	};
 };
--- a/mm/huge_memory.c~mm-move-page-deferred_list-to-folio-_deferred_list
+++ a/mm/huge_memory.c
@@ -2756,9 +2756,9 @@ int split_huge_page_to_list(struct page
 	/* Prevent deferred_split_scan() touching ->_refcount */
 	spin_lock(&ds_queue->split_queue_lock);
 	if (folio_ref_freeze(folio, 1 + extra_pins)) {
-		if (!list_empty(page_deferred_list(&folio->page))) {
+		if (!list_empty(&folio->_deferred_list)) {
 			ds_queue->split_queue_len--;
-			list_del(page_deferred_list(&folio->page));
+			list_del(&folio->_deferred_list);
 		}
 		spin_unlock(&ds_queue->split_queue_lock);
 		if (mapping) {
@@ -2873,8 +2873,8 @@ static unsigned long deferred_split_scan
 	struct pglist_data *pgdata = NODE_DATA(sc->nid);
 	struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
 	unsigned long flags;
-	LIST_HEAD(list), *pos, *next;
-	struct page *page;
+	LIST_HEAD(list);
+	struct folio *folio, *next;
 	int split = 0;
 
 #ifdef CONFIG_MEMCG
@@ -2884,14 +2884,13 @@ static unsigned long deferred_split_scan
 
 	spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
 	/* Take pin on all head pages to avoid freeing them under us */
-	list_for_each_safe(pos, next, &ds_queue->split_queue) {
-		page = list_entry((void *)pos, struct page, deferred_list);
-		page = compound_head(page);
-		if (get_page_unless_zero(page)) {
-			list_move(page_deferred_list(page), &list);
+	list_for_each_entry_safe(folio, next, &ds_queue->split_queue,
+							_deferred_list) {
+		if (folio_try_get(folio)) {
+			list_move(&folio->_deferred_list, &list);
 		} else {
-			/* We lost race with put_compound_page() */
-			list_del_init(page_deferred_list(page));
+			/* We lost race with folio_put() */
+			list_del_init(&folio->_deferred_list);
 			ds_queue->split_queue_len--;
 		}
 		if (!--sc->nr_to_scan)
@@ -2899,16 +2898,15 @@ static unsigned long deferred_split_scan
 	}
 	spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
 
-	list_for_each_safe(pos, next, &list) {
-		page = list_entry((void *)pos, struct page, deferred_list);
-		if (!trylock_page(page))
+	list_for_each_entry_safe(folio, next, &list, _deferred_list) {
+		if (!folio_trylock(folio))
 			goto next;
 		/* split_huge_page() removes page from list on success */
-		if (!split_huge_page(page))
+		if (!split_folio(folio))
 			split++;
-		unlock_page(page);
+		folio_unlock(folio);
 next:
-		put_page(page);
+		folio_put(folio);
 	}
 
 	spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
_

Patches currently in -mm which might be from willy@infradead.org are

buffer-add-b_folio-as-an-alias-of-b_page.patch
buffer-replace-obvious-uses-of-b_page-with-b_folio.patch
buffer-use-b_folio-in-touch_buffer.patch
buffer-use-b_folio-in-end_buffer_async_read.patch
buffer-use-b_folio-in-end_buffer_async_write.patch
page_io-remove-buffer_head-include.patch
buffer-use-b_folio-in-mark_buffer_dirty.patch
gfs2-replace-obvious-uses-of-b_page-with-b_folio.patch
jbd2-replace-obvious-uses-of-b_page-with-b_folio.patch
nilfs2-replace-obvious-uses-of-b_page-with-b_folio.patch
reiserfs-replace-obvious-uses-of-b_page-with-b_folio.patch
mpage-use-b_folio-in-do_mpage_readpage.patch
mm-memcg-add-folio_memcg_check.patch
mm-remove-folio_pincount_ptr-and-head_compound_pincount.patch
mm-convert-head_subpages_mapcount-into-folio_nr_pages_mapped.patch
doc-clarify-refcount-section-by-referring-to-folios-pages.patch
mm-convert-total_compound_mapcount-to-folio_total_mapcount.patch
mm-convert-page_remove_rmap-to-use-a-folio-internally.patch
mm-convert-page_add_anon_rmap-to-use-a-folio-internally.patch
mm-convert-page_add_file_rmap-to-use-a-folio-internally.patch
mm-add-folio_add_new_anon_rmap.patch
page_alloc-use-folio-fields-directly.patch
mm-use-a-folio-in-hugepage_add_anon_rmap-and-hugepage_add_new_anon_rmap.patch
mm-use-entire_mapcount-in-__page_dup_rmap.patch
mm-debug-remove-call-to-head_compound_mapcount.patch
hugetlb-remove-uses-of-folio_mapcount_ptr.patch
mm-convert-page_mapcount-to-use-folio_entire_mapcount.patch
mm-remove-head_compound_mapcount-and-_ptr-functions.patch
mm-reimplement-compound_order.patch
mm-reimplement-compound_nr.patch
mm-convert-set_compound_page_dtor-and-set_compound_order-to-folios.patch
mm-convert-is_transparent_hugepage-to-use-a-folio.patch
mm-convert-destroy_large_folio-to-use-folio_dtor.patch
hugetlb-remove-uses-of-compound_dtor-and-compound_nr.patch
mm-remove-first-tail-page-members-from-struct-page.patch
doc-correct-struct-folio-kernel-doc.patch
mm-move-page-deferred_list-to-folio-_deferred_list.patch
mm-huge_memory-remove-page_deferred_list.patch
mm-huge_memory-convert-get_deferred_split_queue-to-take-a-folio.patch
mm-convert-deferred_split_huge_page-to-deferred_split_folio.patch